Operating mechanism for an electric circuit breaker



E. J. FRANK 3,

OPERATING MECHANISM FOR AN ELECTRIC cmcurr BREAKER 2 Sheets-Sheet 1 Dec.3, 1963 Filed Feb. 14, 1961 a m M 6 I I P L m :"9 V 1.6 n Mr N all w aa? V? t 4 1mm M M. NW0 m H. .5

Dec. 3, 1963 E. J. FRANK 3,113,191

OPERATING MECHANISM FOR AN ELECTRIC CIRCUIT BREAKER Filed Feb. 14, 19612 Sheets-Sheet 2 Inventor: Edward J. -Frank,

by 611cm,

Attovneg.

United States Patent 3,113,191 OPERATING MECHANESM FOR AN ELECTRECtCIRCUlT BREAKER Edward J. Frank, Springfield, Pa, assignor to GeneralElectric Company, a corporation oft New York Filed Feb. 14, 1961, Ser.No. 89,233 7 Claims. (Cl. Mitt-$2) This invention relates to anoperating mechanism for an electric circuit breaker and, moreparticularly, to an operating mechanism in which large amounts ofkinetic energy are stored during the initial and intermediate stages ofcircuit-breaker closing motion, so as to be available for overcoming thehigh opposing forces that may be encountered during the final stages ofclosing motion.

In the type of operating mechanism that this invention is concernedwith, there is a rotatable cam driven through reduction gearing by anelectric motor. This cam is utilized for imparting circuit breakerclosing forces to a linkage coupled to the usual movable contact of thecircuit breaker. As the circuit breaker closing operation progressesthrough the initial and intermediate stages, the motor accelerates to arelatively high speed, thereby storing large amounts of kinetic energyin the moving parts of the mechanism connected to the cam. This storedenergy is available to overcome any opposing forces that may beenecountered near the end of the closing stroke. Upon completion of theclosing stroke, the unused kinetic energy stored behind the camcontinues rotating the cam independently of the linkage. After a slightamount of such overtravel, however, the cam is stopped by braking meanswhich dissipates the unused kinetic energy.

In a mechanism of this character it is highly desirable that overtravelof the cam be limited to a rather narrow range. Otherwise, continuedmotion of the cam could carry it into positions in which it wouldinterfere with the ability of the mechanism to perform a subsequentclosing operation. This problem of precisely controlling the amount ofovertravel is complicated by the fact that there may be widely varyingamounts of kinetic energy to dissipate from one operation to the next.For example, the breaker could be closed either on a deenergized powerline, which would involve no magnetic opposing forces, or on a shortcircuit, which would involve very large magnetic opposing forces; andthe amount of excess energy remaining to be dissipated would be widelydifferent for these two cases. As another example, the source of voltagefor the motor may be subject to wide variations that could produceappreciable differences in the motor speed and, hence, the kineticenergy to be dissipated under diferent voltage conditions. Prior brakingschemes of which I am aware have not been as precise as desired incontrolling the amount of overtravel under such widely varying kineticenergy conditions, particularly where the maximum permissible amount ofovertravel is small and the maximium amounts of kinetic energy arerelatively large.

Accordingly, an object of my invention is to precisely control suchovertravel under widely varying kinetic energy conditions, even wherethe maximum permissible amount of overtravel is quite small and theamounts of kinetic energy involved may sometimes be quite large.

Another object is to provide braking means which can compensate forvarying amounts of kinetic energy by applying a braking force thatautomatically varies in magnitude directly with respect to the amount ofkinetic energy to be dissipated, so that when relatively large amountsof kinetic energy are to be dissipated, relatively large braking forceswill automatically be available.

Another object is to incorporate such braking means in such a mannerthat it will not interfere with attaining the high-speed travel of thecam that is required to develop 3-,l 13,191 Patented Dec. 3, 1963 icethe large amounts of kinetic energy that might be necessary for closing.

Another object is to provide braking means of the above character whichrequires no special brake-releasing means when it is desired to resumemotor operation after braking has been completed.

In carrying out my invention in one form, I provide a linkage fortransmitting force for closing a circuit breaker and a rotatable maincam'for transmitting circuit-breaker closing force to the linkage. Therotatable main cam is coupled to motor means that is operable uponenergizaton to supply closing force to the main cam. After the motormeans has driven the main cam into a predetermined position followinginitiation of a closing operation, the motor means is deenergized andbraking force is thereafter applied to the motor means when the closingoperation is completed. This braking force is derived from braking meanscomprising an auxiliary cam coupled to the main cam for rotation at thesame angular speed as the main cam. The braking means also includes adashpot having a reciprocable piston that is retarded during motion inone direction. Rotary motion of the auxiliary cam drives the dashpotpiston in its direction of retarded motion during travel of theauxiliary cam occurring after the motor is deenergized and after closingof the circuit breaker is completed, whereby to dissipate the kineticenergy stored in the motor means and to stop the main cam in a terminalposition. Reclosing of the circuit breaker is effected by causing themotor to drive the main cam through continued rotary motion past saidterminal position into said predetermined position.

For a better understanding of my invention, reference may be had to thefollowing description taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a schematic view of one form of circuit breaker operatingmechanism embodying my invention. In FIG. 1 the operating mechanism isshown in its open position.

FIG. 2 illustrates the operating mechanism of FIG. 1 shortly after ithas been tripped to open from its closed position.

FIG. 3 shows the operating mechanism of FIG. 1 in its closed position.

Referring now to FIG. 1, the circuit breaker shown therein comprises aset of stationary contacts 12, connected in a power line 14 and amovable bridging contact 16, movable into and out of engagement withsaid stationary contacts 12. The movable bridging contact 16 is securedto the left-hand end of a reciprocable operating rod 18 of insulatingmaterial, which is pivotally connected at its right-hand end to a crank20. This crank 20 is pivotally mounted on a stationary pivot 22. Themova ble contact 16 is biased toward its open position of FIG. 1 bymeans of a suitable opening spring 21, shown as a tension springconnected to the crank 20.

For transmitting closing thrust to the operating rod 13 the contacts 16,there is provided a conventional trip-free linkage L which comprises apair of toggle links 23 and 24-, pivotally joined together at a knee 25.One of the toggle links 23 is pivotally connected at its opposite end tothe lower end of crank 20 by means of pivot pin 27. The other togglelink 24 is pivotally connected by pivot pin 28 to the upper end of aguide link 29. This guide link 29 is pivotally supported at its lowerend on a fixed fulcrum 30. The pivot pin 28 carries a latch roller 31which cooperates with a suitable trip-latch 32, which is arranged to beoperated in response to predetermined circuit conditions by means of asuitable conventional tripping solenoid 34. In the disclosed embodiment,the coil of this solenoid 34 is shown connected across the secondary 35of a current transformer inductively coupled to the power line 14 so asto cause operation of the solenoid in response to over-currents in thepower line 14. Other conventional tripping schemes could, of course, beused. So long as the trip latch remains in the latched position shown inFIG. 3, the toggle 23, 24 is capable of transmitting thrust to themovable contact-actuating rod 18. Thus, when the knee 25 is lifted fromthe position shown in FIG. 1, the toggle 23, 24 is extended and drivesthe crank in a clockwise direction about its pivot 22 and the rod 18 tothe right toward closed position against the bias of opening spring 21.

This lifting of knee is produced by the action of a rotatable main cam40 cooperating with the usual roller 42 which is mounted at the knee 25.When the main cam 40 is rotated clockwise from its solid line positionof FIG. 1 into its dotted line position of FIG. 3 by means soon to bedescribed, it lifts the knee 25, thereby extending the toggle 23, 24 andclosing the breaker. The position occupied by the parts of the linkage Lwhen the breaker is in its fully-closed position is shown in solid linesin FIG. 3. It will be apparent from FIG. 3 that closing action hasresulted in the knee 25 of the toggle being driven slightly past a deadcenter position, i.e., past a reference line connecting the axes ofpivots 28 and 29, so that there is no tendency of toggle 23, 24 toreturn to its retracted position of FIG. 3 when the application ofclosing force to the roller 42 is discontinued. There is a slighttendency for the toggle 23, 24 to collapse upwardly, but this isresisted by a suitable stop 44 co-acting with the roller 42.

Tripping open of the circuit breaker is effected by energizing thesolenoid 34 sufliciently to drive the triplatch 32 clockwise about itsstationary pivot 46 against the bias of a suitable reset spring 47.Should the latch 32 be tripped when the circuit breaker is closed, oreven during the closing stroke, the pivot 28 will be freed by suchtripping action, thus no longer serving as a stationary reaction pointfor the toggle 23, 24. This will render the toggle 23, 24 inoperative totransmit thrust to the movable contact rod 18, and, as a result, theopening spring 21 will be free to drive the movable bridging contact 16into its open position.

The position of the parts shortly after such tripping of latch 32 hasoccurred is shown in FIG. 2. The latch 32, having been moved off thelatch roller 31, is no longer capable of restraining the pivot 28 in itsfixed position of FIG. 3. This has permitted the opening spring 21 todrive the crank 26 counterclockwise about its stationary pivot 22,forcing the entire toggle 23, 24 to the right. The roller 42 rolls alongthe stop 44 until the toggle knee 25 shifts to a position below thereference line connecting pivots 27 and 28, at which time the knee 25 ofthe toggle is free to move downwardly, allowing the toggle 23, 24 tocollapse downwardly at the knee toward its dotted line position of FIG.2. Such collapse of the toggle 23, 24 allows the crank 22 to movefurther counterclockwise under the influence of opening spring 21, thusallowing for further circuit breaker opening. A typical final positionof the linkage at the end of the opening operation is shown in dottedlines in FIG. 2.

For returning the linkage to a thrust-transmitting condition after ithas been tripped open, a reset spring 49 is provided. This reset spring49 cooperates with theguide link 29 to return the guide link to itslatched position of FIG. 1 after tripping has occurred. Thus, in FIG. 1,the linkage L is shown in an open and reset position.

For driving the main cam 49 through a ciosing cycle, e.g., in aclockwise direction from its solid line position of FIG. 1 into itsdotted line position of FIG. 3, an electric motor 59 is provided. Thismotor 5 acts through suitable reduction gearing 52 to drive in aclockwise direction a rotatable shaft 54 to which the main cam 49 issecured. The motor accelerates the cam 49 to a relatively high speed asthe closing stroke progresses so that large amounts of kinetic energyare stored in the moving parts coupled to the cam. This kinetic energyis available to overcome the increasing opposition of the opening spring21 and also the high magnetic opposing forces that would be encounteredat the end of the closing stroke should a fault be present on the powerline 14. When the main cam 40 enters its dotted line position of FIG. 3and thus completes a breaker-closing operation; the motor is deenergizedby means of a suitable limit switch 56 (controlled by a cam 107 securedto shaft 54). But any unused kinetic energy that remains after the motor50 is deenergized acts to continue rotation of the main cam 40 clockwisepast its dotted line position of FIG. 3.

One of the problems that the present invention is concerned with isdissipating this excess kinetic energy and stopping the main cam 40within a rather narrow range of angular positions. Unless thisovertravel of the main cam is precisely controlled, the cam can moveinto positions where it would interfere with the ability of themechanism to perform a subsequent closing operation. For example, themain cam d0 might move into a position that would block resetting of thelinkage L to its thrust-transmitting condition, or it might move into anexcessively advanced final position just ahead of the dotted lineposition of FIG. 3 that would interfere with a subsequent closingoperation. With respect to this latter condition, if, on a subsequentclosing operation, cam travel prior to reaching the closing position isexcessively restricted, there will be insufficient opportunity to attainthe speeds needed for closing under all conditions.

For stopping the main cam 49 within the required narrow range of angularpositions, I provide braking means in the form of a dashpot 60 and anauxiliary cam 62 for transmitting energy from the main cam 46 to thedashpot 6 The dashpot 69 comprises a cylinder 63 filled with a suitableliquid to a level above the highest position of the piston and areciprocable piston 64 slidably mounted in the cylinder. Downward motionof the piston 64 is retarded by the liquid in the cylinder disposedbeneath the piston, with the extent of such retardation being controlledby a small metering opening 65 extending through the piston. Upwardmotion of the piston can take place without significant retardation dueto a large port 66 extending through the piston. A suitable check valve67 controlling the flow of liquid through port 66 allows liquid to flowfreely thereth-rough from the top side to the bottom side of the piston64 during such upward piston motion. This check valve 67 blocks flow ina reverse direction through the port 66, thereby preventing liquid fromflowing downward motion of the piston. A piston reset spring 68positioned beneath the piston 64 acts independently of the auxiliary camto quickly return the piston to its uppermost position (against shoulder69) when downward force is no longer being applied to the piston. Thisquick reset action assures that the piston will be in its uppermostposition in readiness for a braking operation whenever the main cam 46enters its dotted line position of FIG. 3.

For transmitting energy from the auxiliary cam 62 to the piston 64, aroller 70 coupled to the piston rod 71 is provided. This roller 76 isrotatably mounted on a pin 72 carried by a link 73 that is pivotallyconnected at 74 to the upper end of piston rod '71. A guide link 75,pivotally connected atone end to the pin 72 and pivotally mounted at itsother end on a stationary fulcrum 76, serves to guide the roller 70 andto maintain it in thrusttransmitting relationship relative to the pistonrod 71.

In the illustrated embodiment of my invention, the auxiliary cam 62 iscontoured in such a manner that all but about 60 degrees of its outerperiphery is generally uniformly spaced from its axis of rotation. Thisgenerally uniform radius portion of the auxiliary cam 62 is referred tohereinafter as the dwell portion of the cam. The remaining 6 0 degreesof periphery contains a projecting cam portion 79 having a graduallycurved contour through the port during on one side of a high point 80and an approximately radially-extending contour on the other side of ahigh point 8t Shortly after the main cam 4t passes clockwise through thedotted line position of :FlG. 3 during a closing operation, theprojecting portion 79 of the auxiliary cam 62 is just beginning todepress the roller 70 and dashpot piston 64 connected thereto. Asdescribed hereinabove, this downward motion of the dashpot piston 64- isopposed by the liquid beneath the piston, and a powerful retarding forceis thus applied to the main cam 40 through the dashpot piston 64', andthe auxiliary cam '62. The magnitude of this retarding force varies as adirect function of the square of the piston velocity. Hence, the higherthe speed of the main cam 46 as it passes through the dotted lineposition of FIG. 3, the greater will be the retarding force developed bythe dashpot. The dashpot, in effect, compensates for variations in theamount of kinetic energy to be dissipated by applying a [retarding forcethat varies in magnitude as a direct function of the amount of kineticenergy. Thus, the tendency for the higher amounts of excess kineticenergy to produce greater amounts of overtravel is effectively offset bythe greater retarding force. This compensating effect enables thedashpot to stop the cam within a narrow range of angular positions forall magnitudes of excess kinetic energy that will normally beencountered.

The magnitude of the excess kinetic energy depends primarily upon thevoltage that is applied across the terminals of the motor 51) and uponthe magnitude of current encountered upon closing. in one typicalapplication of my circuit breaker, the motor voltage can vary betweennormal limits of 90 and 130 volts, and the magnitude of the currentencountered upon closing can vary from zero to heavy short circuitcurrents corresponding to the rated making current of the circuitbreaker. It will therefore be apparent that the braking means 62, 60might be called upon to dissipate widely varying amounts of excesskinetic energy. In one typical embodiment of my invention, the disclosedbraking means has been capable of limiting the final position of the camunder all normally encountered excess energy conditions to a range of 45degrees. The auxiliary cam 62 is so shaped that for maximum excesskinetic energy conditions, i.e., closing with maximum voltage on adeenergized power line, motion of the auxiliary cam 62 is terminatedappreciably before the high point 80 of the cam 62 reaches the roller'70.

Assume now that the breaker has been tripped open and has thereafterreset into its position of FIG. 1 under the influence of its resetspring 49 and that it is desired to reclose the circuit breaker. Themotor 50 would be energized by closing a switch 85 (in a manner soon tobe described), and such switch-closing would complete an energizingcircuit for the motor through switch 85 and motor 59 across theterminals 86 and $7 of a control voltage source. The motor would respondto completion of this circuit by driving the main cam 45} clockwise fromits initial solid line position of FIG. 1, through its dotted lineposition of FIG. 1, and then into its dotted line position of FIG. 3.Until the high point 80 of the auxiliary cam 62 moves past the roller 76during this clockwise closing motion, the dashpot 60 would have atendency to retard such closing motion. This tendency is considerablylessened, however, by the fact that the initial speed of the main cam 40is relatively low inasmuch as some initial travel is required before themotor can bring its load up to an appreciable speed. Since this initialtravel is at a relatively low speed, the retarding force exerted by thedashpot is also quite low, thus permitting the motor to develop someinitial speed without excessive retardation from the dashpot. When thehigh point 80 of the auxiliary cam 62 passes the roller 70, the dashpotpiston 64 is released from driven relationship with the auxiliary cam 62and further clockwise motion of the main cam 4d can occur withoutopposition from the dashpot 6th until the closing operation isessentially completed. It will be apparent that no specialbrake-releasing means is needed to enable the motor to drive theauxiliary cam 62 past the dashpot roller 70 during this early portion ofa closing operation. Even though no such brake-release has occurred, themotor is able to drive the auxiliary cam 62 past the dashpot withoutundue opposition due to the low retarding forces that the dashpot exertswhen the speed of its piston 64 is low.

During the above-described clockwise motion when the auxiliary cam 62 iscontacting the roller 70 and during about degrees of added clockwiserotation, no appreciable opposing force is being transmitted through thelink-age L to the main earn 4% of the circuit breaker. This follows fromthe fact that the effective working surface of the main cam 40 duringthis extended interval is substantially uniformly spaced from the axisof rotation of the main cam. More specifically, just past the highestpoint $8 on projecting portion 89 of the main cam there is a generallyuniform radius dwell portion 90 of approximately degrees which isarranged to contact the roller 4-2 of the linkage L during this period.Since, by reason of this dwell 9i), no effort is being made to lift theroller 42 during this interval, no appreciable amount of power is beingtransmitted to the linkage L and thus no appreciable opposing force istransmitted through the linkage L to the main cam 4% during thisinterval. The absence of such opposing force contributes in an importantmanner to the ability of the motor to develop the required speed andkinetic energy before closing is attempted. When the dwell portion ofthe cam has finally been driven clockwise past the roller 42 of thelinkage L, a cam portion of gradually increasing radius comes intooperation and lifts roller 42 to close the breaker. The kinetic energythat the cam and its driving means 54}, 52 had acquired prior to thislifting action and the additional kinetic energy developed as thelifting action progresses provides sufficient kinetic energy to closethe breaker positively and firmly even against heavy short circuitcurrents. As the cam moves through the dotted line position of FIG. 3upon completion of the closing operation, the motor is deenergized bythe limit switch 56 and the excess kinetic energy that remains after theclosing operation is dissipated by the dashpot 60, all as describedhereinabove.

A significant feature of my braking means 60, 62 is that it is appliedto the driven end of the power transmission between the motor 5%) andthe main cam 40'. Since this driven end of this power transmission makesonly one revolution during each circuit-breaker closing operation, thebraking means 6t), 62 applies its retarding force only during theportion of the closing operation when it is needed. On the other hand,had the braking means been applied directly to the motor shaft, whichmakes numerous revolutions during each closing operation, the brakingforce would have been applied and released repetitively during theclosing operation, thus interfering with attainment of the desired highspeeds. Additionally, the fact that the brake means 6%), 62 is on thedriven shaft makes it easier to provide a precise angular relationshipbetween the auxiliary cam 62 and the main cam 40, so that braking forcecan be applied at a precisely-located angular position of the main cam40.

It is to be noted that the braking function is involved in only about 60degrees of the total 360 degrees available for the closing operationinasmuch as the dashpot 6% is applying braking force only during thislimited interval. Since only this relatively small portion of the total360 degrees available for closing is consumed by the braking function, arelatively large portion of the remaining angular motion remainsavailable to permit the motor to accelerate the cam d0 unopposed by thelinkage L so that it can develop the high speed and kinetic energyneeded for closing under severe short circuit conditions, particularlywhen the motor voltage is relatively low. Thus, because the brake means60, 62 is exceptionally effective and requires only a small amount ofangular 7 movement to perform its intended function, the duty imposed onthe motor in closing is considerably reduced.

It is important, however, that the braking force not be applied sosuddenly as to cause damage to the reduction gearing 52 or other partsof the mechanical transmission through excessive loads resulting fromsudden dissipation of the stored kinetic energy. To this end, theauxiliary cam 62 is so contoured that the maximum braking torquedeveloped by the braking means 60, 62 does not exceed the maximum torquethat can be developed by the motor at the completion of a closingoperation, i.e., the torque developed at the cam shaft 54 by the motorupon closing on a deenergized power circuit With maximum control voltageapplied to the motor. For example, in one typical embodiment of myinvention the maximum motor torque at the cam shaft 54 is 600pound-inches whereas the maximum braking torque is 500 pound-inches.

The electric control for the motor 50 may be of any suitableconventional form. In the illustrated embodiment of the invention,however, this control comprises a motor control relay 190 that isarranged to close its contacts 85 when energized. If the circuit breakeris open, as shown in FIG. 1, closing of the contacts 85 completes anenergizing circuit through the motor that extends from the positiveterminal 86 of the source of control voltage, through the contacts 85 ofthe motor relay, then through the motor 50 and a normally closed limitswitch 106 to the negative terminal 87 of the control voltage source.Completion of this energizing circuit causes the motor to drive the maincam 40 clockwise from its solid line position of FIG. 1 through itsdotted line position of FIG. 1. By this time, a seal-in circuit has beencompleted around the contacts 35 of the motor relay 1% by means of thelimit switch 56 controlled by cam Hi7 secured to the cam shaft d. Thus,when the contacts 35 of the motor relay drop out (as soon to bedescribed), the motor 50 remains energized through the limit switch 56.When the motor drive the main cam 40 clockwise through its dotted lineposition of FIG. 3, the limit switch 56 opens, thereby deenergizing themotor, as described hereinabove. The other limit switch 106, which isopened by closing of the circuit breaker, opens immediately thereafter,thereby providing assurance that the motor 51) will be deenergized assoon as the breaker is closed.

For establishing an energizing circuit for the motor control relay 1%,there is provided a closing control switch 110 that is operable eithermanually or by suitable means capable of producing automatic reclosingof the main circuit breaker. This closing control switch 110 isconnected in a circuit 111 that extends from the positive terminal ofthe control voltage source, through the closing control switch 119, ananti-pump device 112, a [2 switch 114 sensitive to position of thebreaker, and the coil of the motor starting relay 100 to the negativeterminal of the control voltage source. When the closing control switch110 is closed, it completes this energizing circuit 111, thereby pickingup the motor relay 1% and initiating motor operation. The motor beginsthe breaker closing operation and as the breaker approaches closedposition, the b switch 114 opens, interrupting this operation-initiatingcircuit 111 and dropping out the motor relay 100. The motor operationcontinues, however, because the sealin circuit through limit switch 56is then closed. When the motor has completely closed the breaker, thelimit switches 56 and 106 open to deenergize the motor, as previouslydescribed.

The anti-pump device 112 serves to prevent inadvertent repetitiveclosing operations should the closing control switch 110 be held closedwhen the breaker trips open upon being closed on a fault. This device112 serves to maintain the closure-initiating circuit 111 open after ithas produced one circuit breaker closing, so long as the closing controlswitch lit) is held closed. This anti-pump device 112 may be of anysuitable conventional form, such as, for example, that shown in US.Patent 2,381,336,

Coggeshall, assigned to the assignee of the present invention.

In some applications of my operating mechanism, it may happen that ifthe dashpot reset spring 68 is heavy enough to effect the desired highspeed resetting of the piston 64 to its uppermost position after beingreleased, then such spring would also be heavy enough to slowly rotatethe auxiliary cam 62 and the other mechanisms 40, 52, Sit back towardits dotted line position of FIG. 3 after completion of a brakingoperation. An undesirable condition could result from allowing thisreverse rotation to carry the cam 40 completely into the dotted lineposition of FIG. 3 inasmuch as resetting of the linkage L could behampered by the presence of the cam 40 in the dotted line position ofFIG. 3. My mechanism is arranged to prevent this condition fromoccurring by reason of the fact that upward motion of the dashpot piston64 is blocked by the stop 69 substantially ahead of the point that thepiston 64 would be required to reach in order to completely return thecam 40 to its dotted line position. When the piston 64 reaches the stop69, the cam 44) still has not reached a position where it couldinterfere with resetting of the linkage L should such resetting berequired. Additionally, when the piston 64 reaches the stop 6%, thecontrol cam Hi7 still has not reached a position that would permitclosing of the motor control switch 56. Closing of this control switch56 under these conditions is desirably avoided since such closing couldlead to an undesirable hunting condition.

Although in the illustrated mechanism the motor cutoff switch 56 isarranged to deenergize the closing motor 50 at about the time theclosing stroke is completed, it is to be understood that this switchcould be arranged to deenergize the motor considerably ahead of thispoint, with reliance being placed on the relatively great inertia of themotor 50 and reduction gearing 52 to carry the circuit breaker throughits complete stroke. Thus, in a modified embodiment of my invention, thecut-off switch 56 is opened ahead of the point in the closing stroke atwhich a prestrike could occur between the main contacts 16, 12 of thebreaker when closing on a fault. The inertia of the moving parts ofmotor 59 and gearing 52 is sufiicient to complete the closing stroke,even against heavy short circuit currents. Arranging the cut-off switch56 to operate at this earlier point in the closing stroke provides evenfurther assurance that the dashpot reset spring 68 will not accidentallycause reclosing of the switch 56 as a result of its above-describedtendency to produce reverse rotation after the braking operation.

The fact that my braking scheme requires no electrical control power forits proper operation is another highly desirable feature. In thisregard, should electrical control power he lost during a closingoperation, the brake would still be capable of acting in its intendedmanner. With regard to the operation of motor 50 under such conditionsthe inertia of the parts connected to the cam 40 is high enough toassure successful completion of a closing operation should control powerbe lost during the latter stages of the closing operation. Thus, even ifelectrical control power would be so lost, successful completion of theclosing operation and subsequent braking in the desired manner wouldstill occur.

While I have shown and described particular embodiments of my invention,it will be obvious to those skilled in the art that various changes andmodifications may be made without departing from my invention in itsbroader aspects, and I, therefore, intend in the appended claims tocover all such changes and modifications as fall within the true spiritand scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A circuit breaker operating mechanism comprising a linkage fortransmitting force for closing said circuit breaker, means including arotatable main cam for trans mitting circuit-breaker closing force tosaid linkage, mo-

tor means operable upon energization to supply closing force to saidrotatable main cam, means for deenergizing said motor means uponmovement of said main cam into a predetermined position followinginitiation of a circuitbreaker closing operation, an auxiliary cammechanically coupled to said main cam for rotation at the same angularspeed as said main cam, a liquidcontaining dashpot having a reciprocablepiston that is retarded by said liquid during motion in one direction,means for causing rotary motion of said auxiliary cam to drive saiddashpot piston in its direction of retarded motion during travel of saidauxiliary cam occurring after deenergization of said motor means andafter closing of said circuit breaker is completed whereby to dissipatethe kinetic energy stored in said motor means and stop said main cam ina terminal position, and means for causing said motor means to producereclosing of said circuit breaker by driving said main cam throughcontinued rotary motion past said terminal position into saidpredetermined position, said dashpot piston being free from drivenrelationship with said auxiliary cam during the major portion ofmovement of said main cam between said terminal position and saidpredetermined position.

2. The operating mechanism of claim 1 in which said piston has a normalinitial position that it occupies when said main cam passes through apreselected position at which closing of said circuit breaker iscompleted and in which means is provided for resetting said piston tosaid normal initial position during a closing operation, saidpiston-resetting means acting essentially independently of saidauxiliary cam once said dashpot piston is released from drivenrelationship with said auxiliary cam, said piston being essentiallyunretarded during piston-resetting movement to enable said resettingmeans to restore said piston substantially to said initial position bythe time said main cam enters said preselected position at which closingis completed.

3. The operating mechanism of claim 1 in which said main cam is soshaped that no substantial closing force is applied to said linkageduring predetermined initial travel upon energization of said motormeans, said predetermined initial travel acting to release said dashpotpiston from driven relationship with said auxiliary cam and beingsufliciently extensive to drive said auxiliary cam into a positionwherein said dashpot is ineffective to retard continued rotary motion ofsaid main cam until said main cam has driven said linkage substantiallyinto the circuit-breaker closed position.

4. The operating mechanism of claim 1 in which said main cam is soshaped that no substantial closing force is applied to said linkageduring predetermined initial travel upon energization of said motormeans, said predetermined initial travel acting to release said dashpotpiston from driven relationship with said auxiliary cam and beingsufiiciently extensive to drive said auxiliary cam into a positionwherein said dashpot is ineffective to retard continued rotary motion ofsaid main cam until sai dmain cam has driven said linkage substantiallyinto the circuit-breaker closed position, said predetermined initialtravel also being sufficiently extensive to allow said motor means todrive said main cam a substantial distance past the point at which saiddashpot becomes ineffective to retard said main cam.

5. The operating mechanism of claim 1 in which said piston has a normalinitial position that it occupies when braking is initiated; in whichresetting means is provided for returning said piston to said normalinitial positon during a closing operation, said resetting means tendingafter a braking operation and before a subsequent closing operation toreturn said main cam toward a position in which said main cam couldinterfere with resetting of said linkage to a thrust-transmittingcondition after an opening operation; and in which means is provided forblocking return movement of said main cam into said interferingposition.

6. A circuit breaker operating mechanism comprising a linkage fortransmitting force for closing said circuit breaker, means including arotatable main cam for trans mitting circuit breaker closing force tosaid linkage, motor means adapted to be energized from a source ofvoltage that is subject to variations between predetermined minimum andmaximum values, means for transmitting closing power from said motormeans to said main cam, means for deenergizing said motor means afterinitiation of a closing operation and upon movement of said main caminto a predetermined position, an auxiliary cam mechanically coupled tosaid main cam for rotation at the same angular speed as said main cam, aliquid-containing dashpot having a reciprocal piston that is retarded bysaid liquid during motion in one direction, means for causing rotarymotion of said auxiliary cam to drive said dashpot piston in itsdirection of retarded motion during travel of said auxiliary camoccurring after said main cam has driven said linkage into thecircuit-breaker closed position whereby to dissipate the kinetic energystored in said motor means and stop said main cam, said auxiliary cambeing so shaped that said dashpot continues to oppose rotary motion ofsaid main cam until said ro tary motion is terminated even when saidcircuit breaker is closed against no electrical load with said maximumvalue of voltage on said motor means and means for causing said motormeans to produce reclosing of said circuit breaker by driving said maincam through continued rotary motion past said terminal position intosaid predetermined position, said dashpot piston being free from drivenrelationship with said auxiliary cam during the major portion ofmovement of said main cam between said terminal position and saidpredetermined position.

7. The operating mechanism of claim 6 in which the maximum brakingtorque applied by said dashpot to said main cam is less than the maximumtorque that said motor applies to said cam when closing under maximumvoltage conditions on a deenergized power line.

References Cited in the file of this patent UNITED STATES PATENTS1,376,436 Hipple May 3, 1921 2,053,961 Linde Sept. 8, 1936 2,307,567Coggeshall et al. Jan. 5, 1943 2,361,739 Bobst Oct. 31, 1944 2,680,164Lennox June 1, 1954 2,895,570 Kury July 21, 1959 2,920,607 Barkan Jan.12, 1960

1. A CIRCUIT BREAKER OPERATING MECHANISM COMPRISING A LINKAGE FORTRANSMITTING FORCE FOR CLOSING SAID CIRCUIT BREAKER, MEANS INCLUDING AROTATABLE MAIN CAM FOR TRANSMITTING CIRCUIT-BREAKER CLOSING FORCE TOSAID LINKAGE, MOTOR MEANS OPERABLE UPON ENERGIZATION TO SUPPLY CLOSINGFORCE TO SAID ROTATABLE MAIN CAM, MEANS FOR DEENERGIZING SAID MOTORMEANS UPON MOVEMENT OF SAID MAIN CAM INTO A PREDETERMINED POSITIONFOLLOWING INITIATION OF A CIRCUITBREAKER CLOSING OPERATION, AN AUXILIARYCAM MECHANICALLY COUPLED TO SAID MAIN CAM FOR ROTATION AT THE SAMEANGULAR SPEED AS SAID MAIN CAM, A LIQUID-CONTAINING DASHPOT HAVING ARECIPROCABLE PISTON THAT IS RETARDED BY SAID LIQUID DURING MOTION IN ONEDIRECTION, MEANS FOR CAUSING ROTARY MOTION OF SAID AUXILIARY CAM TODRIVE SAID DASHPOT PISTON IN ITS DIRECTION OF RETARDED MOTION DURINGTRAVEL OF SAID AUXILIARY CAM OCCURRING AFTER DEENERGIZATION OF SAIDMOTOR MEANS AND AFTER CLOSING OF SAID CIRCUIT BREAKER IS COMPLETEDWHEREBY TO DISSIPATE THE KINETIC ENERGY STORED IN SAID MOTOR MEANS ANDSTOP SAID MAIN CAM IN A TERMINAL POSITION, AND MEANS FOR CAUSING SAIDMOTOR MEANS TO PRODUCE RECLOSING OF SAID CIRCUIT BREAKER BY DRIVING SAID